Lisa Mullen lectures MTT1 Flashcards
biochemistry
4 things energy is required for
> motion (muscle contraction)
transport (of ions/molecules across membranes)
biosynthesis of essential metabolites
thermoregulation
Why does Mg2+ deficiency make you feel tired
Mg2+ forms complex with ATP inside cells, deficiency impairs virtually all metabolism
A) What class of enzyme transfers electrons
B)What class of enzyme transfers functional groups
A) oxidoreductases
B) transferases
Which vitamin is needed for coenzyme:
A) FAD
B) NAD+
A) Riboflavin (B2)
B) Niacin
Glycolysis:
A) which enzyme phophorylates glucose into glucose-6-phosphate
B) Which enzyme is involved in the committed step, and what is the reaction
A) Hexokinase
B) PFK-1 catalyses fructose-6-phosphate into fructose 1,6 bisphosphate
*both priming reactions
Glycolysis:
Which reaction does Pyruvate kinase catalyse
phosphoenolpyruvate into pyruvate
Inside the mitochondria, what is the link reaction
include the enzyme that catalyses it
pyruvate + CoA + NAD+ ——-> acetyl CoA + NADH + H+
catalysed by PDH complex
Which 5 coenzymes make up PDH complex, and which 4 vitamins are vital for this complex
TPP, NAD+, CoA, FAD, Lipoic acid
Thiamine for TPP
Riboflavin for FAD
Niacin for NAD
Pantothenate for CoA
What does ACIKSSFMO stand for (order of intermediates in TCA cycle)
Acetyl CoA Citrate Isocitrate alpha-Ketoglutarate Succinyl CoA Succinate Fumarate L-Malate Oxaloacetate
What are the two shuttles used to regenerate NAD+ via transport of 2 electrons
Where is each one mainly found
How many moles of ATP is produced
1) glycerol-3-phosphate shuttle, in brain and muscle
2) malate-aspartate shuttle, in liver and heart
1. 5 or 2.5 moles ATP
Which 4 complexes make up the ETC
Which soluble proteins link them
Complex I, II, III, IV
Linked by ubiquinone (coenzyme Q) Cytochrome C (links III and IV)
Name the antiporter protein that transports ADP3- into matrix in exchange for ATP4- out of matrix
adenosine nucleotide translocase
Name of symporter that transports both phosphate and H+ into the matrix
phosphate translocase
2 functional domains of ATP synthase
Fo: an oligomycin-sensitive proton channel
F1: an ATP synthase
What is Atractyloside
found in thistle, specific inhibitor of adenosine nucleotide translocase
The different subunits that comprise Fo and F1 domains of ATP synthase
Fo: 13-15 a, b and c subunits
F1: 9 subunits of alpha 3, beta 3, gamma, delta and reverse E
2 uncoupling reagents that dissipate H+ gradient allowing H+ back into matrix via a diff route that is not ATP synthase, thus severing linnk between e- flow and ATP synthesis. Releasing energy as heat
occurs naturally: UCP1 (thermogenin): found in brown adipose tissue and has specific H+ chanel for H+ to flow back into matrix, releasing heat as it does so. Important in newborns to keep them warm
occurs unnaturally: DNP: a weight loss drug. A weak acid that crosses membranes ‘ferrying’ H+ across with it. Each DNP collects H+ from intemrembrane space, crosses inner membrane and deposits H+ in matrix. Can return to collect another proton
Compare nuclear and mitochondrial genome
Nuclear: Introns present 3% coding dna Histones associated Maternal/paternal inheritance 20,000-30,000 genes encoded
Mitochondrial genome: no introns or histones 93% coding dna Maternal inheritance only genes code for: 13 respiratory chain proteins 2 rRNA proteins 22 tRNA proteins (tRNA structure different)
What are oxidative phosphorylation enzyme defects strongly associated with
alzheimers, parkinsons, type II diabetes
heteroplasmy
presence of more than one type of mt DNA within a cell/ individual. It is important in determining the severity of diseases
What is threshold effect
a disease will only present itself if 70% or more of mitochondria in a cell was mutant
What does LHON stand for and what is it
Lebers hereditary optic neuropathy
single base change in mt gene ND4 (Arg>His) in complex I of ETC. Not enough ATP generated = damage to optic nerve = blindness
What does MERRF stand for and what is it
Myoclonus epilepsy with ragged-red fibre
a point mutation in mt gene encoding tRNA specific for lysine, disrupts synthesis of proteins essential for OXPHOS = abnormal shaped mitochondria in skeletal muscle.
Ragged red fibres is red clumps of abnormal mitochondria that appears on staining
What is MELAS syndrome, what does it stand for
>symptoms in childhood
Mitochondrial encephalomyopathy lactic acidosis
mt gene dysfunction effecting complex I and tRNA, effects brain and skeletal muscle
childhood symptoms: lactic acidosis, stroke-like symptoms with muscle weakness, seizures leading to loss of vision, involuntary muscle spasms (myoclonus), dementia
What does KSS stand for and what is it
> symptoms
Kearns-sayre syndrome
results from 5kb deletion of mt genome, onset before 20
symptoms: dementia, retinitis pigmentosa
mt myopathies treatment options
occupational/ physical therapy: may extend range of muscle movement
vitamin therapies: riboflavin, creatinine, CoQ, C, K and carnitine may help
2 strategies to prevent mt myopathies
mitochondrial gene replacement (pronuclear stage)
maternal spindle transfer
glucose is polar, so how enters cells via glucose transport proteins (gluts)
give 5 examples and where they are found
glut 1: found in erythrocytes, muscle, brain, kidney, colon, placenta
glut 2: found in liver, pancreatic cells
glut 3: found in brain
glut 4: found in skeletal muscle, adipose tissue
glut 5: small intestine (fructose transporter)
Where does pentose phosphate pathway branch from
two products of pentose phosphate pathway And what they’re used for
Branches from glycolysis at G-6-P
Products:
1)ribose phosphate: used to synthesise RNA and DNA
2) NADPH: used for reductive biosynthesis and to maintain redox balance of cell
what makes glycogen a GOOD energy store. What makes it a BAD energy store
GOOD: highly branched, large number of ends for phosphorylase and glycogen synthase to ensure rapid breakdown and resynthesis
BAD: glucose is hydrophillic, it associates with water increasing overall weight and bulk
2 mechanisms of glycogenolysis
1) glycogen phosphorylase breaks bonds between alpha1,4 linked glucose by addition of phosphate to produce glucose-1-phosphate
2) alpha1,6 bonds requires debranching enzyme alpha1,6 glucosidase which is a hydrolysis reaction producing free glucose
allosteric regulation of glycogen phosphorylase in muscle
AMP activates phosphorylase as it is a sign of ATP depletion
ATP and gluc-6-phosphate inhibit phosphorylase as they are a sign of inc energy levels
allosteric regulation of glycogen synthase
activated by gluc-6-phosphate and ATP
In liver, glucose and G-6-P inhibits glycogenolysis
How is glycogen phosphorylase activated by cAMP-dependent phosphorylation
What effect does this cAMP cascade have on glycogen synthase
cAMP cascade leads to phosphorylation of serine in glycogen phosphorylase, this activates glycogen phosphorylase. It is in ‘a’ conformation
opposite effect on glycogen synthase, it converts enzyme to ‘b’ conformation, the less active state
what are main regulatory points for link reaction/ TCA cycle
link reaction: PDH complex
TCA cycle: citrate synthase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase
anaplerotic reactions of TCA cycle
pyruvate replenishes OAA via pyruvate carboxylase
PEP replenishes OAA via PEP carboxylase
Malate is replenished by pyruvate into malate via malic enzyme
Names of complex I,II,III and IV in ETC
I = NADH dehydrogenase II = succinate dehydrogenase III = ubiquinone:cytochrome c oxidoreductase IV= cytochrome oxidase
theory of rotational catalysis
conformation 1: ADP+Pi are bound
conformation 2: ADP+Pi = ATP
conformation 3: ATP released (active site has low affinity for ATP in this formation)
What is mitochondrial genetic bottleneck
The randomness in the way mitochondria is inherited specifically in the oocyte amplification and maturation stage means we can’t predict outcome of mitochondrial inheritance
Functions of liver
Glycogen synthesis
Glycogenolysis
Gluconeogenesis
Fatty acid synthesis from glucose secrete as TAGs in VLDL
Synthesise ketone bodies and secretes into blood as fuel for other tissues
Stores fat soluble vitamins
Why is brain most vulnerable to hypoglycaemia
1) cannot store glucose in significant amounts or synthesise glucose
2) cannot metabolise substrates other than glucose or ketone bodies
3) cannot extract sufficient glucose for their needs at low concentrations because glucose entry into brain is not facilitated by hormones
Immediate and long term effects of insulin
Immediate:
Inc rate of glucose uptake in muscle and adipocytes
Modulation of activity of enzymes involved in glucose metabolism
Long term:
Inc expression of liver enzymes that synthesise glycogen
Inc expression of adipocyte enzymes that synthesise TGs, this inhibits lipolysis in adipose tissue
Functions as growth factor for some cells eg fibroblasts
How is glycogen broken down in muscle vs liver
Muscle: glycogen >gluc 1 phosphate > gluc 6 phosphate > pyruvate > lactate +co2
Liver: glycogen >gluc 1 phosphate > gluc 6 phosphate > glucose via enzyme glucose 6 phosphatase
How does glycogen form in first place
How do branches form
UDP-glucose donates first glucosyl residue and attaches it to aa tyrosine in protein glycogenin. Remaining glucose units added in alpha 1,4 linkage from UDP glucose creating growing chain
Branching enzyme transfers block of 7 residues to growing chain to create new branch with alpha 1,6 linkage. New branch cannot form within 4 residues of existing branch
